Species List

Ferns

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Ferns

The familial taxonomic framework here applied follows Smith & al. (2006). Additional, more recent phylogenetic molecular studies by Schuettpelz & al. (2016) considerably modified this taxonomy, mostly in adopting a much narrower familial and generic concept and thus accepting more families and genera than before. For instance, Woodsiaceae was accepted as a monogeneric family with Athyriaceae (e.g. native Athyrium) and Cystopteridaceae (e.g. native Cystopteris and Gymnocarpium) segregated from it. There is a lot of controversy whether or not too many fern genera are accepted now (compare Schuettpelz & al. 2018 and Christenhusz & Chase 2018).

The Belgian pteridophytes, native as well as non-native, are here classified as follows (familial circumscriptions that differ from Lambinon & al. 2004 are preceded by an *):

13. Leaves usually smaller, never sterile below and fertile above. Sporangia with an annulus ===14

14. Sori not covered by inrolled leaf margin, long and linear, occupying almost entire length of the pinnae of the fertile leaves. Blade of sterile leaf (ob-) lanceolate, more than 3x as long as wide. Margin of the pinnae entire to crenate (native) === Blechnaceae

In addition to the fern species treated here several others are in cultivation in Belgium and might occur as escapes. One of the commonest taxa indoors surely is Nephrolepis (especially N. cordifolia C. Presl and N. exaltata (L.) Schott; Hovenkamp & Miyamoto 2005). Nephrolepis has been accommodated in a separate family (Nephrolepidaceae) or in Dryopteridaceae or Polypodiaceae, although recent phylogenetic studies rather support inclusion in Lomariopsidaceae (Smith & al. 2006). Nephrolepis superficially resembles Polypodium but fronds are longer with much more pinnae, lighter green, always 1-pinnate and sori are always covered by an indusium. Nephrolepis cordifolia and N. exaltata are increasingly found as garden escapes in southern Europe (see for instance Marchetti 1999, Simões da Silva & Domingues de Almeida 2000) and might occur in suitable places where frostbite is unlikely in Belgium as well (basement walls,…). In recent times several other non-native ferns from other genera have been recorded as escapes in neighbouring countries. Clement & Foster (1994) cite for instance species of Phymatodes, Davallia, Cyathea and Dicksonia but these are generally confined to climatically more favourable locations (chiefly in the Channel Islands). See also Grenfell (1983) for an account of exotic ferns running wild in the British Isles. More interesting is a recent record of Doodia aspera R. Brown on a London wall (Edgington 2005). In the Netherlands Marsilea quadrifolia L. (Marsileaceae) recently occurred along river Waal (Drok & Weeda 1999), probably as an escape from cultivation although native status has been suggested. It is unmistakable with its 4-foliolate leaves and long-creeping rhizomes. Osmunda regalis L. is a locally frequent native species in woodlands and heaths on peaty soil. It is also cultivated for ornament and at least part of the Belgian populations is probably non-native. Their exact identity possibly requires additional research since several other taxa of Osmunda are involved. Page & Bennell (1986) cite the more or less distinct Osmunda cinnamomea L. and O. claytoniana L. (the latter has been reported from the Netherlands; van Ooststroom 1970). Finally, cultivated populations of Osmunda regalis could represent non-native varieties and should be checked carefully. Botrychium lunaria (L.) Swartz is a very rare, endangered native species. Two additional taxa of this genus have been reported from Belgium: Botrychium matricariifolium (A. Braun ex Döll) Koch, an extinct native and B. simplex E. Hitchc. The latter is represented in Belgium by a single, enigmatic record in 1908 in the sea dunes in Knokke, possibly introduced with planted Swedish pines (De Langhe 1989) or as an exceedingly rare, extinct native (Leten 1992). Finally, several additional pteridophytes have recently been recorded as escapes in the (heated) greenhouses of the Botanic Garden in Meise. Psilotum nudum (L.) Beauv. (Psilotaceae) is a common pot weed and probably occurs in other greenhouses in Belgium. Cyclosorus dentatus (Forssk.) Ching. (syn.: Christella dentata (Forssk.) Brownsey et Jermy, Thelypteris dentata (Forssk.) St John) (Thelypteridaceae) also behaves like a weed and occurs in greenhouses where it is not cultivated. Further records include Pellaea rotundifolia (Forst.) Hook. (Pteridaceae) and Microsorum pteropus (Blume) Copeland (syn.: Polypodium pteropus Blume) (Polypodiaceae).